The Oregon Public Utility Commission voted Tuesday to lower payments to participants in the state’s feed-in-tariff program for solar energy as a hedge against the fledgling program’s rampant popularity.

The program – a pilot until 2014 – is intended to spur solar development by offering payments for solar power. The payments are made by participating utilities to the owners of solar energy systems.

Customers of Portland General Electric, Pacific Power and Idaho Power can lock in rates for 15 years, so long as they build solar systems with a capacity smaller than 100 kilowatts. Larger systems lock in rates through a competitive bidding process.

So far, the program has proven so popular with consumers that its capacity was subscribed in just 15 minutes in the first enrollment period July 1. Rates were then set between 55 and 65 cents per kilowatt-hour.

On Tuesday, however, the Public Utility Commission decreased the rate by 10 percent.

For customers of PGE and Pacific Power, that means that the payback rate will be between 49 and 58 cents per kilowatt-hour – still a screaming deal given that PGE and Pacific Power customers pay about 10 cents per kilowatt-hour.

The rate reduction intentionally slows the rush, but it isn't all just lemons. The move is instead part of a delicate inquiry into solar development, intended to allow utilities and solar providers to find the sweet spot between up-front costs and long-term payoffs to entice solar consumers.

"That's one of the pieces we wanted to learn from the pilot program, what’s the magic number?" he said.

Public Utility Commission spokesman Bob Valdez said the rates could see more adjustments upward or downward as the pilot continues. Rate adjustments are carefully scripted according to whether capacity in the feed-in-tariff program is fully subscribed at each enrollment period, and how quickly.

"We're learning as we go. That's really what pilot projects were designed to generate in terms of a benefit," he said.

Customers who don't get a reservation can also try again. The Oregon utilities plan to open offer two enrollment periods annually, for a total of eight enrollment periods through 2014, when the pilot project ends. Idaho Power will offer one last shot at enrollment in April 2011.